Mods:
CO 104 st on needle 2.5. Join in the round. Knit 1 twisted (knit in the back loop), purl 1 = repeat until the ribbing measures about 4.5 cms.

Switching to needle 3, continue in stockinette st and increase with 1 st after every 8 stitches on the first round=117 st total. Place a marker at the beg. of next round. Knit 7 st, wrap and turn. Purl to middle marker, purl 7 st, wrap and turn. Knit to middle marker, knit 12 st, w&t. Purl to middle marker, purl 12 st, w&t. Knit to middle marker, knit 17 st, w&t. Purl to middle marker, purl 17 st, w&t.

Continue in stockinette in the round, knitting 2 st together where there is an opening from the w&t = 116 st in total. Continue until the front piece measures about 17 cms incl. ribbing. Place a marker right opposite the original middle marker (58 st apart). Knit to 1st before marker (both of them), inc 1, knit 1, slip marker, knit 1, inc 1. Repeat 5 times. Place half of the stitches on a stitch holder or scrap yarn and knit the legs separately: On first round; knit 1, knit 2 tog; repeat. Switch to double pointed needles when necessary. Knit 2 rounds. Knit 1, knit 2 tog on the next round. Bind off with Jeny’s surprisingly stretchy bind off. Repeat with second leg.

Knit an i-cord like this: https://www.purlsoho.com/create/2006/09/29/i-cord/